Stirling refrigerating machine

ABSTRACT

Insertion holes ( 3   c,    4   e ) into which a connection pipe ( 9 ) are inserted are formed from a casing ( 3 ) to a cylinder ( 4 ). The connection pipe ( 9 ) has a flange ( 9   a ) formed on the outer periphery at a set distance from the end of the connection pipe ( 9 ). With the flange ( 9   a ) in contact with the wall outer surface of the casing ( 3 ), the end part of the connection pipe ( 9 ) is inserted into the insertion holes ( 3   c,    4   e ). Between the flange ( 9   a ) and the wall outer surface of the casing ( 3 ), an O-ring ( 01 ) is fit so as to surround an internal passage ( 9   f ) of the connection pipe ( 9 ). Another O-ring ( 02 ) is fit between the end part of the connection pipe ( 9 ) and the insertion hole ( 4   e ) of the cylinder ( 4 ).

TECHNICAL FIELD

This invention relates to a Stirling refrigerating machine in which acompressor is connected to an expander through a connection pipe, andparticularly relates to improvements of a sealing structure provided ata joint between the compressor and the connection pipe.

BACKGROUND ART

A free displacer type Stirling refrigerating machine has beenconventionally known as one of small size refrigerating machines whichproduce cold conditions at an extremely low temperature level. Such arefrigerating machine is disclosed in Japanese Patent ApplicationLaid-Open Gazette No. 6-174321. The refrigerating machine is so composedthat a compressor for compressing a gas refrigerant and an expander forexpanding the gas refrigerant discharged from the compressor areconnected to each other through a connection pipe.

Below, description will be made about the structure of the compressor.

As shown in FIG. 6, the compressor (a) includes a gastight casing (b), acylinder (c) provided in the casing (b), a pair of pistons (e, e)reciprocatably fit in the cylinder (c) to form a compression room (d) inthe cylinder (c), and linear motors (f, f) for reciprocating the pistons(e, e) respectively. The cylinder (c) has cylindrical recesses (c1, c1).The recesses (c1, c1) are formed around the compression room (d) in amanner coaxial with the cylinder (c).

The linear motor (f) has an annular permanent magnet (g) disposed in therecess (c1). The permanent magnet (g) generates a magnetic field withthe cylinder (c) serving as a yoke. An inverted-cup-shaped bobbin (h) isreciprocatably placed in the recesses (c1). The bobbin (h) is providedwith a drive coil (i). The drive coil (i) is opposed to the permanentmagnet (g). The bobbin (h) is fixed at a center thereof to the piston(e). A lead (k) for supplying a current to the drive coil (i) is led outof the bobbin (h). The lead (k) is connected to a terminal (m) mountedon the casing (b). The outer bottom surface of the bobbin (h) (a sideopposite to the piston) and the inner bottom surface of the casing (b)are bridged with a piston spring (j) formed of a coil spring. The pistonspring (j) resiliently supports the piston (e) so as to allowreciprocating motions of the piston (e).

A gas passage (c2) is formed in the cylinder (c) and the casing (b). Thegas passage (c2) is open at one end thereof to the compression room (d)and at the other end to the outer surface of the casing (b).

The compressor (a) is connected to one end of a connection pipe (n), sothat the internal passage of the connection pipe (n) is communicatedwith the gas passage (c2). The other end of the connection pipe (n) isconnected to an expander (not shown).

In operating the refrigerating machine, an alternating current of aspecific frequency is supplied to the drive coils (i, i) through theleads (k, k). Thereby, a magnetic field generated around the drive coils(i, i) acts to reciprocate the bobbins (h, h). Attendantly, the pistons(e, e) lineally reciprocate in the cylinder (c) in opposite directions,so that a compressed gas generates in the compression room (d) incycles. A pressure of a gas refrigerant thus compressed is introduced tothe expander through the connection pipe (n). Thus, a high pressure anda low pressure repeatedly acts on the expander. In the expander, a gasrefrigerant is expanded so that a cold condition is produced.

PROBLEM THAT THE INVENTION IS TO SOLVE

In such kind of refrigerating machine, it is required to maintain itsoperating performance at a high level. To satisfy the requirement, acompressed gas generated in the compressor (a) must be efficientlytransferred to the expander. To cope with this, necessary positionssurrounding the gas passage (c2) each have a sealing structure forpreventing a leakage of a compressed gas.

Below, the conventional sealing structure will be described.

As shown in FIG. 7, O-rings (o, p, p) are disposed at a joint betweenthe casing (b) and the connection pipe (n) and a contact part betweenthe casing (b) and the cylinder (c), respectively. First, description ismade about the sealing structure of the joint between the casing (b) andthe connection pipe (n). A mount (b1) having a plain mounting surface isformed on the outer surface of the casing (b), while a plate-shapedflange (n1) is formed at one end of the connection pipe (n). A sealinggroove (n2) is formed on the flange (n1). The sealing groove (n2) isannular and surrounds the internal passage of the connection pipe (n). Asingle O-ring (o) is inserted in the sealing groove (n2). The mount (b1)and the flange (n1) each have unshown screw holes. The gas passage (c2)is aligned with the internal passage of the connection pipe (n), and inthis state the flange (n1) is brought into contact with the mountingsurface of the mount (b1). Thereafter, screws (q, q) are screwed in boththe screw holes, so that the connection pipe (n) is connected to thecompressor (a). In this structure, since the single O-ring (o) isinterposed between the flange (n1) and the mount (b1), this prevents agas refrigerant flowing through the gas passage (c2) from leaking out ofa clearance between the flange (n1) and the mount (b1) (See arrow A inFIG. 7).

Next, description is made about the sealing structure of the contactpart between the casing (b) and the cylinder (c). Sealing grooves (c3,c3) are formed at both sides (right and left in FIG. 7) of the gaspassage (c2) of the cylinder (c). The sealing grooves (c3, c3) areformed over the circumference of the cylinder (c). The cylinder (c) isinserted into the casing (b) with O-rings (p, p) (two in total) fit intothe sealing grooves (c3, c3) respectively. In this structure, the twoO-rings (p, p) are interposed between the outer periphery of thecylinder (c) and the inner periphery of the casing (b). Accordingly, agas refrigerant flowing through the gas passage (c2) is prevented fromleaking out of a clearance between the cylinder (c) and the casing (b)to the inner space of the casing (b) (See arrow B in FIG. 7).

However, the above sealing structure has the following problems: In thestructure, a sealed part between the casing (b) and the cylinder (c) isformed over the circumference of the cylinder (c). In other words, theO-rings (p, p) each having a large diameter identical with the outerdiameter of the cylinder (c) are used. Therefore, a sealed area becomeslarge. This makes it difficult to obtain a sufficient reliability of asealing function, that is, the possibility that a gas refrigerant mayleak out of the contact part between the casing (b) and the cylinder (c)to the inner space of the casing (b) is increased.

The present invention has been made in view of the above problem. Anobject of the invention is to increase a reliability of a sealingfunction of a contact part between a casing and a cylinder in acompressor of a Stirling refrigerating machine.

DISCLOSURE OF INVENTION SUMMARY OF THE INVENTION

In the present invention, an end part of a connection pipe is insertedinto insertion holes formed in a casing and a cylinder respectively.Then, a sealing function is provided to a joint between the end part ofthe connection pipe and the cylinder. In this arrangement, a sealed areais decreased, resulting in increase in reliability of the sealingfunction of the contact part between the casing and the cylinder.

FEATURES OF THE INVENTIONS

More specifically, a solution taken in claim 1 of the invention isdescribed below. As shown in FIGS. 1 and 3, the solution is directed toa Stirling refrigerating machine having a compressor (1) and an expander(2). The Stirling refrigerating machine premises the followingstructure: The compressor (1) comprises, a cylinder (4) fit into acasing (3), a piston (6) which is inserted into the cylinder (4) so asto be capable of reciprocating motion relative to the cylinder (4) andforms a compression room (7) between the piston (6) and the cylinder(4), resilient means (14) for resiliently supporting the piston (6) onthe casing (3), and drive means (10) for driving the piston (6) intoreciprocating motion relative to the cylinder (4). The compression room(7) is communicated with the expander (2) through a connection pipe (9).The drive means (10) relatively reciprocates the piston (6) with respectto the cylinder (4) so that a compressed fluid generated in thecompression room (7) is introduced into the expander (2) through theconnection pipe (9).

The casing (3) has an insertion hole (3 c) which penetrates the casing(3) and whose one end is open to an outer surface of the casing (3),while the cylinder (4) has an insertion hole (4 e) which is communicatedat one end with the insertion hole (3 c) of the casing (3) and at theother end with the compression room (7).

Further, a compressor (1) side joint end part of the connection pipe (9)is inserted into the insertion hole (3 c) of the casing (3) and theinsertion hole (4 e) of the cylinder (4) to communicate an internalpassage (9 f) of the connection pipe (9) with the compression room (7).

Furthermore, sealing means (02, 28) are interposed between thecompressor (1) side joint end part of the connection pipe (9) and theinsertion hole (4 e) of the cylinder (4).

A solution taken in claim 2 of the invention is so composed that in theStirling refrigerating machine of claim 1, as shown in FIG. 3, anannular sealing groove (9 d) is formed on one of the outer periphery ofthe connection pipe (9) located in the insertion hole (4 e) of thecylinder (4) and the inner periphery of the insertion hole (4 e) of thecylinder (4) so as to extend in a circumferential direction of theperiphery. The sealing means is formed of an O-ring (02) fit into thesealing groove (9 d).

A solution taken in claim 3 of the invention has, in the Stirlingrefrigerating machine of claim 1, the following structure: As shown inFIG. 4, the cylinder (4) is provided with a gas passage (8) coaxial withthe insertion hole (4 e) of the cylinder (4) and having a smallerdiameter than the insertion hole (4 e) of the cylinder (4). The gaspassage (8) is communicated at one end with the compression room (7) andat the other end with the insertion hole (4 e) through a step part (4f). The inner periphery of the insertion hole (4 e) of the cylinder (4)is formed into a female thread (4 g), while the outer periphery of thecompressor (1) side joint end part of the connection pipe (9) located inthe insertion hole (4 e) of the cylinder (4) is formed into a malethread (9 e) screwed in the female thread (4 g). The sealing means isformed of an O-ring (02) interposed between the end surface of theconnection pipe (9) and the step part (4 f).

A solution taken in claim 4 of the invention has, in the Stirlingrefrigerating machine of claim 1, the following structure: As shown inFIG. 5, the inner periphery of the insertion hole (4 e) of the cylinder(4) is formed into a female thread (4 g), while the outer periphery ofthe compressor (1) side joint end part of the connection pipe (9)located in the insertion hole (4 e) of the cylinder (4) is formed into amale thread (9 e) screwed in the female thread (4 g). The sealing meansis made of an adhesive agent (28) put in a clearance between the femalethread (4 g) and the male thread (9 e).

A solution taken in claim 5 of the invention is so composed that in theStirling refrigerating machine of claim 1, as shown in FIGS. 4 and 5,the connection pipe (9) has a flange (9 a) formed in one piece with theconnection pipe (9) and opposed to the outer surface of the casing (3)and a metal packing (27) is interposed between the outer surface of thecasing (3) and the flange (9 a).

OPERATIONS

In the above-mentioned feature of claim 1 of the invention, when theStirling refrigerating machine is in operation, the drive means (10)causes reciprocating motion of the piston (6) relative to the cylinder(4), so that a pressure of fluid compressed in the compression room (7)is introduced into the expander (2) through the connection pipe (9). Inthis operating condition, the sealing means (02), (28) interposedbetween the compressor (1) side joint end part of the connection pipe(9) and the insertion hole (4 e) of the cylinder (4) prevent the fluidfrom leaking out of a clearance between the connection pipe (9) and thecylinder member (4). A sealed area of the sealing means (02), (28) is acontact part between the connection pipe (9) and the insertion hole (4e) of the cylinder (4). Thus, the sealed area is limited to a small areaof only a part of the outer periphery of the connection pipe (9) therebyimplementing high-reliable sealing.

In the features of claims 2, 3 and 4 of the invention, specificstructures of the sealing means (02), (28) are obtained and therebyimproves the practicality of the sealing structure. Particularly, in thefeatures of claims 3 and 4 of the invention, the male thread (9 e)formed on the outer periphery of the connection pipe (9) is screwed inthe female thread (4 g) formed on the cylinder (4). This eliminates theneed for separate screw structure or the like for mounting theconnection pipe (9) on the cylinder (4). Further, in the feature ofclaim 4 of the invention, the sealing means is made of an adhesive agent(28). This allows the sealing means to display the function ofincreasing a strength of mounting the connection pipe (9) on thecylinder (4) as well as the sealing function.

In the feature of claim 5 of the invention, the function of sealingbetween the connection pipe (9) and the casing (3) is displayed by themetal packing (27) interposed between those members. This provides highsealing performance to the joint of the connection pipe (9) to thecompressor (1) in association with the actions of the other claimsabove-mentioned of the invention.

EFFECTS OF THE INVENTION

According to claim 1 of the invention, an area sealed by the sealingmeans (02), (28) can be limited to a small area of only a part of theouter periphery of the connection pipe (9). This implements a moresecure sealing as compared with the conventional case of providingsealing means over the entire circumference of the cylinder (4).Consequently, the reliability of the sealing function can be increased,thereby maintaining the operating performance of the refrigeratingmachine at a high level.

According to claims 2, 3 and 4 of the invention, the practicality of thesealing structure can be increased. In particular, according to claims 3and 4 of the invention, a simple joint structure and a simple joint workof the connection pipe (9) can be implemented. Further, according toclaims 3 and 4, a joint structure can be formed between the innerperiphery of the insertion hole (4 e) of the cylinder (4) and the outerperiphery of the connection pipe (9). This eliminates the need forproviding a large flange to be joined to the casing on the outerperiphery of the connection pipe as in the conventional case. Inaddition, there is no need for providing, in the casing, a mount andscrew holes for joint of the flange. Accordingly, the thickness of thecasing can be decreased, resulting in downsizing and weight reduction ofthe entire compressor. Furthermore, according to claim 4 of theinvention, the sealing means can have a function of increasing astrength of mounting the connection pipe (9) on the cylinder (4) as wellas the sealing function. Consequently, the joint of the connection pipe(9) can secure the high reliability of the joint state.

According to claim 5 of the invention, in association with the aboveeffects of the claims, the joint of the connection pipe (9) to thecompressor (1) can obtain high sealing performance. This furtherincreases the operating performance of the refrigerating machine.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross section showing the internal structure of a linearmotor compressor.

FIG. 2 is a cross section showing the internal structure of an expander.

FIG. 3 is a cross section showing a joint of a connection pipe to thecompressor of Embodiment 1 of the present invention.

FIG. 4 is a diagram corresponding to FIG. 3 in Embodiment 2 of thepresent invention.

FIG. 5 is a diagram corresponding to FIG. 3 in Embodiment 3 of thepresent invention.

FIG. 6 is a diagram showing a conventional linear motor compressor,which corresponds to FIG. 1.

FIG. 7 is a diagram corresponding to FIG. 3 in the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, description will be made about embodiments of the presentinvention with reference to the drawings.

EMBODIMENT 1

FIGS. 1 and 2 show a linear motor compressor (1) and an expander (2) ofa Stirling refrigerating machine according to the present embodiment,respectively. First, the compressor (1) is described. The compressor (1)is composed of an opposed-piston type reciprocating compressor. Thecompressor (1) has a gastight, cylindrical casing (3). The casing (3)consists of a cylindrical body (3 a) and disc-shaped blocking plates (3b, 3 b) for blocking both end openings of the cylindrical body (3 a). Acylinder (4) is disposed in the casing (3). The cylinder (4) is made ofpure iron. The cylinder (4) has an outer tube (4 a) fixed on the wallinner surface of the casing (3) and an inner tube (4 b) disposed insidethe outer tube (4 a) with a set distance left therebetween. The outertube (4 a) and the inner tube (4 b) are connected to each other througha doughnut-shaped connection part (4 c), so that recesses (4 d) areformed between the outer tube (4 a) and the inner tube (4 b). Therecesses (4 d) each have a cylindrical form coaxial with the cylinder(4). The center of the inner cylinder (4 b) is formed into a pistoninsertion hole (5).

Piston bodies (22, 22) of the piston (6, 6) are inserted into the pistoninsertion hole (5) from the right and left of FIG. 1, respectively. Aspace surrounded by both the piston bodies (22, 22) and the inner tube(4 b) forms a compression room (7). The outer diameter of the pistonbody (22) is formed slightly smaller than the inner diameter of theinner tube (4 b), so that a small clearance of, e.g., approximately 10μm is formed between the piston body (22) and the inner tube (4 b). Thesmall clearance is sealed by an unshown clearance seal or fluid seal,thereby securely holding the hermeticity of the compression room (7).

In the cylinder (4), a gas passage (8) radially extending from thepiston insertion hole (5) is formed. The gas passage (8) is open at aninner end thereof to the compression room (7). The gas passage (8) iscommunicated with an internal passage (9 f) of the connection pipe (9).The compressor (1) and the expander (2) are connected to each otherthrough the connection pipe (9).

The pistons (6, 6) are connected to linear motors (10, 10) as drivemeans for driving the pistons (6, 6) into reciprocating motion,respectively. The linear motors (10, 10) each have a permanent magnet(11) and a coil (12). The permanent magnet (11) is formed of acylindrical magnet externally fit on the outer periphery of the innertube (4 b). In this arrangement, the permanent magnet (11) forms amagnetic circuit with the cylinder (4) serving as a yoke. That is, amagnetic field of a specific intensity is produced between thoseelements.

The pistons (6, 6) are supported to approximately inverted-cup-shapedbobbins (13, 13), respectively. The bobbins (13) each includes acylindrical bobbin body (20) and a disc-shaped piston mounting part (21)provided at one side end of the bobbin body (20) (outer right and outerleft ends of the bobbin bodies (20) of FIG. 1). A recessed coil wrappingpart (20 a) is formed at a position of the outer periphery of the bobbinbody (20) corresponding to the permanent magnet (11). The coil (12) iswrapped around the coil wrapping part (20 a). The center of the pistonmounting part (21) is formed into an opening (21 a) for inserting thepiston body (22) therethrough.

The piston (6) has the piston body (22) in bottomed, cylindrical formand a flange (23) extending from a rear end of the piston body (22)(outer right and outer left ends of the piston bodies (22) of FIG. 1)toward the periphery.

The piston body (22) is inserted through the opening (21 a) until theflange (23) is overlaid on the piston mounting part (21). Then, both themembers (23, 21) are assembled into one piece by screws (N1, N1).

Between the piston (6) and the blocking plate (3 b), a resin-made leadholding member (24) is disposed. The lead holding member (24) holds apart of a lead (15) for supplying an electric current to the coil (12).The lead (15) is connected at an outer end thereof to terminals (26, 26)provided in the blocking plate (3 b) of the casing (3).

In the piston body (22), a spring mounting member (16) having a springmount (16 a) is inserted. At a front end of the piston body (22), athrough hole is formed along the axis of the piston body (22). Thespring mounting member (16) has a female thread formed at a positioncorresponding to the through hole. A screw (N3) is screwed into thefemale thread from the front end of the piston body (22), so that thespring mounting member (16) and the piston (6) are assembled into onepiece. The blocking plate (3 b) of the casing (3) is provided at acenter thereof with a spring mount (3 d) identical in form with thespring mount (16 a). A spring (16) is placed from one to the other ofboth the spring mounts (16 a, 3 d), so that the piston body (22) isresiliently supported in the cylinder member (4) so as to be capable ofreciprocating motion.

Under the above structure, when an alternating current of a specificfrequency (e.g., 50 Hz) is supplied to the coil (12, 12) insynchronization, both the pistons (6, 6) reciprocate in oppositedirections at a natural frequency. As a result, a compressed gasgenerates in the compression room (7) in cycles. The above frequency ofthe alternating current is set in accordance with masses of respectivepistons (6, 6) and a spring constant of the spring (14).

A feature of the present embodiment lies in a joint structure of theconnection pipe (9) to the compressor (1). Below, the joint structure isdescribed with reference to FIG. 3. As shown in the figure, an insertionhole (3 c) is formed in the casing (3). The insertion hole (3 c) isformed in such a manner as to penetrate the casing (3) in a radialdirection (vertical direction of FIG. 3). The insertion hole (3 c) hasthe inner diameter approximately identical with the outer diameter ofthe connection pipe (9). Around the insertion hole (3 c) on the outerperiphery of the casing (3), a mount (17) having a plain mountingsurface (17 a) is formed. An insertion hole (4 e) is formed in thecylinder (4). The insertion hole (4 e) is formed outside from anapproximately middle point in a thickness direction of the cylinder (4).The gas passage (8) is formed inside the insertion hole (4 e). Theinsertion hole (4 e) of the cylinder (4) is identical in diameter withthe insertion hole (3 c) of the casing (3). The insertion hole (4 e) iscommunicated at an outer end thereof with the insertion hole (3 c) ofthe casing (3) and at an inner end thereof with the gas passage (8). Thegas passage (8) is formed smaller in diameter than the insertion holes(3 c, 4 e). Further, the insertion holes (3 c, 4 e) and the gas passage(8) are coaxially arranged in series. In this arrangement, a step part(4 f) is formed between the insertion hole (4 e) of the cylinder (4) andthe gas passage (8).

Meanwhile, the connection pipe (9) has a flange (9 a) contacting themounting surface (17 a) of the mount (17) and an insertion part (9 b)located on an end side from the flange (9 a). The insertion part (9 b)is inserted into the insertion holes (3 c, 4 e). In this state, theflange (9 a) contacts the mounting surface (17 a) of the mount (17).Both the members (9 a, 17) are jointed to each other by screws (N4, N4).A sealing groove (9 c) is formed on the bottom surface of the flange (9a) which contacts the mount (17). The sealing groove (9 c) is annularlyformed so as to surround the insertion part (9 b) of the connection pipe(9). A single O-ring (01) is fit into the sealing groove (9 c). In otherwords, the single O-ring (01) is interposed between the mounting surface(17 a) of the mount (17) and the flange (9 a) of the connection pipe (9)so as to surround the connection pipe (9). This provides the structureof preventing a leakage of a gas refrigerant from a clearance betweenthe connection pipe (9) and the casing (3) to the outside.

A sealing groove (9 d) is also formed at the end of the insertion part(9 b) of the connection pipe (9). The sealing groove (9 d) is formed onthe outer periphery of a portion of the connection pipe (9) located inthe insertion hole (4 e) of the cylinder (4). The sealing groove (9 d)has an annular form over the circumference of the outer periphery of theconnection pipe (9). A single O-ring (02) as a sealing means is fit intothe sealing groove (9 d). In other words, the O-ring (02) is interposedbetween the end of the connection pipe (9) and the cylinder (4) so as tosurround the connection pipe (9). Thereby, sealing is establishedbetween the outer periphery of the connection pipe (9) and the innerperiphery of the insertion hole (4 e) of the cylinder (4). This providesthe structure of preventing a leakage of a gas refrigerant from aclearance between the casing (3) and the cylinder (4) through aclearance between the connection pipe (9) and the insertion hole (4 e).The O-ring (02) has the outer diameter approximately identical with theouter diameter of the connection pipe (9).

Next, description is made about the expander (2) to which a refrigerantis supplied through the connection pipe (9). As shown in FIG. 2, theexpander (2) includes a cylinder (30) and a free displacer (31)reciprocatably inserted into the cylinder (30). The free displacer (31)divides an inner space of the cylinder (30) into an expansion room (30a) and an operational room (30 b). In the operational room (30 b), adisplacer spring (32) formed of a coil spring is disposed. The displacerspring (32) resiliently supports the free displacer (31) to the cylinder(30). The inside of the free displacer (31) is filled with metallic coldstorage material (31 a). The free displacer (31) is provided at anexpansion room (30) side end thereof with a first communication hole (31b). The first communication hole (31 b) allows gas refrigerantcommunication with the expansion room (30 a). On the other hand, thefree displacer (31) is provided at an operational room (30 b) side endthereof with a second communication hole (31 c). The secondcommunication hole (31 c) allows gas refrigerant communication with theoperational room (30 b). The operational room (30 b) is communicatedwith the compression room (7) of the compressor (1) through theconnection pipe (9).

Next, description is made about operations of the Stirling refrigeratingmachine having the above-mentioned structure. During operation, analternating current of a specific frequency (50 Hz) is supplied to boththe coils (12, 12) of the linear motors (10, 10) of the compressor (1)in synchronization. By the supply of the alternating current, a magneticfield generated in the permanent magnet (11) and the cylinder (4) actsto reciprocate the coils (12, 12) and the pistons (6, 6). Thereciprocations of the pistons (6, 6) are motions directed opposite toeach other. In association with these motions, the springs (14, 14)become deformed. Thus, both the pistons (6, 6) synchronously moveforward and backward in the cylinder (4) so that the volume of thecompression room (7) is increased and decreased. Thereby, a pressurewave is produced in the compression room (7) in cycles. In the expander(2), the free displacer (31) reciprocates in the same cycle as in thepressure wave of the compression room (7), thereby causing gasexpansion. The gas expansion in the expander (2) produces a coldcondition. Such a reciprocating motion of the free displacer (31) isrepeated, so that a cold head at the end of the cylinder (30) is cooleddown to an extremely low temperature level.

In the above operation, a comparatively high-pressure gas refrigerantflows through the gas passage (8) and the internal passage (9 f) of theconnection pipe (9). As mentioned above with reference to FIG. 3, thecontact part between the mount (17) of the casing (3) and the flange (9a) of the connection pipe (9), and the joint part between the outerperiphery of the end of the connection pipe (9) and the cylinder (4) aresealed with the O-rings (01, 02), respectively. Further, the O-rings(01, 02) each have a comparatively small diameter and their sealed areasare set small. Accordingly, sufficient sealing functions are displayedin the sealed areas, thereby preventing a leakage of a gas refrigerantin each sealed area.

As mentioned so far, this embodiment is directed to prevent a gasrefrigerant from leaking out of a clearance between the casing (3) andthe cylinder (4). Further, the end part of the connection pipe (9) isinserted into the insertion holes (3 c, 4 e) respectively formed in thecasing (3) and the cylinder member (4). Furthermore, the O-ring (02) isprovided at the joint part between the outer periphery of the end of theconnection pipe (9) and the cylinder (4). That is, the O-ring (02) isformed so as to have a small diameter approximately identical with theouter diameter of the connection pipe (9). This reduces a sealed area,resulting in increase in the reliability of the sealing function.

In this embodiment, the O-ring (02) is fit into the sealing groove (9 d)formed at the end of the insertion part (9 b) of the connection pipe(9). However, this invention is not limited to this structure and may beso composed that an O-ring is fit into a sealing groove formed on theinner periphery of the insertion hole (4 e) of the cylinder (4).

EMBODIMENT 2

Next, description will be made about Embodiment 2 of the invention. Thepresent embodiment is a modification of the sealing structure of thejoint of the connection pipe (9) to the compressor (1). The other partsare the same as in the above-mentioned Embodiment 1. Therefore, here,description is made only about the sealing structure of the joint.

As shown in FIG. 4, a male thread (9 e) is formed on the outer peripheryof the end part of the connection pipe (9) of this embodiment, while afemale thread (4 g) capable of screw-in of the male thread (9 e) isformed on the inner surface of the insertion hole (4 e) of the cylinder(4). The male thread (9 e) at the end part of the connection pipe (9) isscrewed in the female thread (4 g) of the insertion hole (4 e), so thatthe connection pipe (9) is joined to the compressor (1). In this stateof joint, an O-ring (02) is interposed between the end surface of theconnection pipe (9) and the step part (4 f). The O-ring (02) is adjustedso that the outer diameter thereof is approximately identical with theinner diameter of the insertion hole (4 e) of the cylinder (4) and theinner diameter thereof approximately matches the inner diameter of thegas passage (8).

Further, between the flange (9 a) of the connection pipe (9) and themounting surface (17 a) of the mount (17), a metal packing (27) isinterposed. Thereby, a clearance between the connection pipe (9) and thecasing (3) is sealed.

In the above structure, sealing between the mount (17) of the casing (3)and the flange (9 a) of the connection pipe (9) is established by themetal packing (27), while sealing of the joint between the end part ofthe connection pipe (9) and the cylinder (4) is established by theO-ring (02). Also in this embodiment, the O-ring (02) has acomparatively small diameter and therefore a sealed area is set small.Accordingly, a sufficient sealing function can be displayed, therebypreventing a leakage of a gas refrigerant in each sealed are.

EMBODIMENT 3

Next, description will be made about Embodiment 3 of the presentinvention. The present embodiment is a modification of the sealingstructure of the joint between the end part of the connection pipe (9)and the cylinder (4). The other parts are the same as in theabove-mentioned Embodiment 2. Therefore, here, description is made onlyabout the sealing structure of the joint.

As shown in FIG. 5, a clearance between the male thread (9 e) formed onthe outer periphery of the end part of the connection pipe (9) and thefemale thread (4 g) formed in the cylinder (4), is filled with anadhesive agent (28) as a sealing means. The adhesive agent (28)implements the structure of displaying a high sealing function whilesecurely obtaining a joint strength of a part that the male thread (9 e)is screwed in the female thread (4 g). This structure requires noO-ring, so that there is no need for a fitting work of an O-ring. Thissimplifies a work of joining the connection pipe (9) to the compressor(1).

OTHER EMBODIMENTS

The present invention is not limited to a non-contact type compressorwhich is designed to provide a small clearance between the cylinder (4)and the piston (6), that is, is applicable to a contact type compressorin which no small clearance is provided between the cylinder (4) and thepiston (6).

INDUSTRIAL APPLICABILITY

A Stirling refrigerating machine of the present invention is useful for,in particular, application to an opposed-piston type compressor in whichan internal pressure of a compression room is set high. In this case, ahigh-pressure gas produced in the compression room is transferred to anexpander with efficiency.

What is claimed is:
 1. A Stirling refrigeration machine having acompressor (1) and an expander (2), in which said compressor (1)comprises: a cylinder (4) fit into a casing (3); a piston (6) which isinserted into the cylinder (4) so as to be capable of reciprocatingmotion relative to the cylinder (4) and forms a compression room (7)between the piston (6) and the cylinder (4); resilient means (14) forresiliently supporting the piston (6) on the casing (3); and drive means(10) for driving the piston (6) into reciprocating motion relative tothe cylinder (4), wherein the compression is communicated with theexpander (2) through a connection pipe (9), and wherein the drive means(10) relatively reciprocates the piston (6) with respect to the cylinder(4) so that a compressed fluid generated in the compression room (7) isintroduced into the expander (2) trough the connection pipe (9), theimprovement characterized in that: the casing (3) has an insertion hole(3 c) which penetrates the casing (3) and whose one end is open to theouter surface of the casing (3), while the cylinder (4) has an insertionhole (4 e) which is communicated at one end with the insertion hole (3c) of the casing (3) and at the other end the compression room (7); acompressor (1) side joint end part of the connection pipe (9) isinserted into the insertion hole (3 c) of the casing (3) and theinsertion hole (4 e) of the cylinder (4) to communicate an internalpassage (9 f) of the connection pipe (9) with the compression room (7);and sealing means (02, 28) are interposed between an end part of theconnection pipe (9), which is connected to said compressor (1), and theinsertion hole (4 e) of the cylinder (4) to prevent a leakage of thefluid from a clearance between the casing (3) and the cylinder (4) intothe casing (1).
 2. The Stirling refrigerating machine of claim 1,wherein an annular sealing groove (9 d) is formed on one of the outerperiphery of the connection pipe (9) located in the insertion hole (4 e)of the cylinder (4) and the inner periphery of the insertion hole (4 e)of the cylinder (4) so as to extend in a circumferential direction ofthe periphery, and the sealing means is formed of an O-ring (02) fitinto the sealing groove (9 d).
 3. The Stirling refrigerating machine ofclaim 1, wherein the cylinder (4) is provided with a gas passage (8)coaxial with the insertion hole (4 e) of the cylinder (4) and having asmaller diameter than the insertion hole (4 e) of the cylinder (4), saidgas passage (8) being communicated at one end with the compression room(7) and at the other end with the insertion hole (4 e) through a steppart (4 f), the inner periphery of the insertion hole (4 e) of thecylinder (4) is formed into a female thread (4 g), while the outerperiphery of the compressor (1) side joint end part of the connectionpipe (9) located in the insertion hole (4 e) of the cylinder (4) isformed into a male thread (9 e) screwed in the female thread (4 g), andthe sealing means is formed of an O-ring (02) interposed between the endsurface of the connection pipe (9) and the step part (4 f).
 4. TheStirling refrigerating machine of claim 1, wherein the inner peripheryof the insertion hole (4 e) of the cylinder (4) is formed into a femalethread (4 g), while the outer periphery of the compressor (1) side jointend part of the connection pipe (9) located in the insertion hole (4 e)of the cylinder (4) is formed into a male thread (9 e) screwed in thefemale thread (4 g), and the sealing means is made of an adhesive agent(28) put in a clearance between the female thread (4 g) and the malethread (9 e).
 5. The Stirling refrigerating machine of claim 1, whereinthe connection pipe (9) has a flange (9 a) formed in one piece with theconnection pipe (9) and opposed to the outer surface of the casing (3),and a metal packing (27) is interposed between the outer surface of thecasing (3) and the flange (9 a).